Abstract: Many meta-analysis, large cohort studies, and experimental studies suggest that chronic alcohol consumption increases the risk of gastric and colon cancer Ethanol is metabolized by alcohol dehydrogenases (ADH), catalase or cytochrome P450 2E1 (CYP2E1) to acetaldehyde, which is then further oxidized to acetate by aldehyde dehydrogenase (ALDH) Acetaldehyde has been classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen to humans The acetaldehyde level in the stomach and colon is locally influenced by gastric colonization by Helicobacter pylori or colonic microbes, as well as polymorphisms in the genes encoding tissue alcohol metabolizing enzymes, especially ALDH2 Alcohol stimulates the uptake of carcinogens and their metabolism and also changes the composition of enteric microbes in a way to enhance the aldehyde level Alcohol also undergoes chemical coupling to membrane phospholipids and disrupts organization of tight junctions, leading to nuclear translocation of β-catenin and ZONAB, which may contributes to regulation of genes involved in proliferation, invasion and metastasis Alcohol also generates reactive oxygen species (ROS) by suppressing the expression of antioxidant and cytoprotective enzymes and inducing expression of CYP2E1 which contribute to the metabolic activation of chemical carcinogens Besides exerting genotoxic effects by directly damaging DNA, ROS can activates signaling molecules involved in inflammation, metastasis and angiogenesis In addition, alcohol consumption induces folate deficiency, which may result in aberrant DNA methylation profiles, thereby influencing cancer-related gene expression

Abstract: The non-oxidative dehydrogenation of ethanol to acetaldehyde has long been considered as an important method to produce acetaldehyde and clean hydrogen gas. Although monometallic Cu nanoparticles have high activity in the non-oxidative dehydrogenation of ethanol, they quickly deactivate due to sintering of Cu. Herein, we show that adding a small amount of Ni (Ni0.01Cu − Ni0.001Cu) into Cu to form highly dilute NiCu alloys dramatically increases the catalytic activity and increases their long-term stability. The kinetic studies show that the apparent activation energy decreases from ∼70 kJ/mol over Cu to ∼45 kJ/mol over the dilute NiCu alloys. The improved performance is observed both for nanoparticles and nanoporous NiCu alloys. The improvement in the long-term stability of the catalysts is attributed to the stabilization of Cu against sintering. Our characterization data show that Ni is atomically dispersed in Cu. The comparison of the catalytic performance of highly dilute alloy nanoparticles with nanoporous materials is useful to guide the design of novel mesoporous catalyst architectures for selective dehydrogenation reactions.

Abstract: The thermotolerant yeast Kluyveromyces marxianus shows promise as an industrial host for the biochemical production of fuels and chemicals. Wild-type strains are known to ferment high titers of ethanol and can effectively convert a wide range of C5, C6, and C12 sugars into the volatile short-chain ester ethyl acetate. Strain engineering, however, has been limited due to a lack of advanced genome-editing tools and an incomplete understanding of ester and ethanol biosynthesis. Enabled by the design of hybrid RNA polymerase III promoters, this work adapts the CRISPR–Cas9 system from Streptococcus pyogenes for use in K. marxianus. The system was used to rapidly create functional disruptions to alcohol dehydrogenase (ADH) and alcohol-O-acetyltransferase (ATF) genes with putative function in ethyl acetate and ethanol biosynthesis. Screening of the KmATF disrupted strain revealed that Atf activity contributes to ethyl acetate biosynthesis, but the knockout reduced ethyl acetate titers by only ~15%. Overexpression experiments revealed that KmAdh7 can catalyze the oxidation of hemiacetal to ethyl acetate. Finally, analysis of the KmADH2 disrupted strain showed that the knockout almost completely eliminated ethanol production and resulted in the accumulation of acetaldehyde. Newly designed RNA polymerase III promoters for sgRNA expression in K. marxianus enable a CRISPR–Cas9 genome-editing system for the thermotolerant yeast. This system was used to disrupt genes involved in ethyl acetate biosynthesis, specifically KmADH1–7 and KmATF. KmAdh2 was found to be critical for aerobic and anaerobic ethanol production. Aerobically produced ethanol supplies the biosynthesis of ethyl acetate catalyzed by KmAtf. KmAdh7 was found to exhibit activity toward the oxidation of hemiacetal, a possible alternative route for the synthesis of ethyl acetate.

Abstract: Acetaldehyde is a highly reactive compound that causes various forms of damage to DNA, including DNA adducts, single- and/or double-strand breaks (DSBs), point mutations, sister chromatid exchanges (SCEs), and DNA-DNA cross-links. Among these, DNA adducts such as N²-ethylidene-2'-deoxyguanosine, N²-ethyl-2'-deoxyguanosine, N²-propano-2'-deoxyguanosine, and N²-etheno-2'-deoxyguanosine are central to acetaldehyde-mediated DNA damage because they are associated with the induction of DNA mutations, DNA-DNA cross-links, DSBs, and SCEs. Acetaldehyde is produced endogenously by alcohol metabolism and is catalyzed by aldehyde dehydrogenase 2 (ALDH2). Alcohol consumption increases blood and salivary acetaldehyde levels, especially in individuals with ALDH2 polymorphisms, which are highly associated with the risk of squamous cell carcinomas in the upper aerodigestive tract. Based on extensive epidemiological evidence, the International Agency for Research on Cancer defined acetaldehyde associated with the consumption of alcoholic beverages as a "group 1 carcinogen" (definite carcinogen) for the esophagus and/or head and neck. In this article, we review recent advances from studies of acetaldehyde-mediated carcinogenesis in the squamous epithelium, focusing especially on acetaldehyde-mediated DNA adducts. We also give attention to research on acetaldehyde-mediated DNA repair pathways such as the Fanconi anemia pathway and refer to our studies on the prevention of acetaldehyde-mediated DNA damage.

Abstract: Combined application of kinetic measurements, SSITKA and deuterium tracing techniques allowed to elucidate the mechanism of the key steps of butadiene synthesis over silver promoted zirconia catalysts, including ethanol dehydrogenation, acetaldehyde aldol condensation, and crotonaldehyde reduction with ethanol, and to determine the rate-limiting step of the process. We show for the first time that butadiene synthesis involves two independent catalytic cycles: i) dehydrogenation of ethanol into acetaldehyde over metal sites, and ii) acetaldehyde/ethanol transformation into butadiene over Lewis acidic sites. The first cycle implies ethanol dehydrogenation into acetaldehyde via concerted cleavage of CH 2 and OH groups, followed by the fast desorption of the products formed into the gaseous phase. The second cycle starts with the activation of acetaldehyde over Lewis acid sites through enolization and its interaction with another acetaldehyde molecule from the gaseous phase via Eley-Rideal mechanism. The formed 3-hydroxybutanal further dehydrates into crotonaldehyde. The aldol condensation step was proposed to be rate-determining. Further transformation of crotonaldehyde proceeds through Langmuir-Hinshelwood mechanism, involving the interaction of crotonaldehyde with ethanol over a Lewis site via a six-member ring transition state. Subsequently, crotyl alcohol dehydrates into butadiene, and acetaldehyde adsorbed over Lewis sites initiates the next catalytic cycle. The proposed molecular-level mechanism gives insights into rational design of efficient catalysts for the ethanol conversion into butadiene.

Abstract: For the effect of structural features on the catalytic performance of the conversion of ethanol and acetaldehyde to butadiene to be investigated, a series of MgO–SiO2 catalysts with different structural properties were synthesized by tuning the calcination temperature, investigated, and characterized. The best butadiene selectivity of 80.7% appears for the MgO–SiO2 catalyst calcined at 500 °C using a mixture of acetaldehyde/ethanol/water (22.5:67.5:10 wt %) as feed. Addition of the appropriate amount of water (10 wt %) improved butadiene selectivity by inhibiting the formation of 1-butanol and C6 compounds. Results from XRD, FT-IR, and 29Si MAS NMR indicate the generation of a significant amount of amorphous magnesium silicates along with few crystalline magnesium silicates for the catalyst calcined at 500 °C. XPS results indicate that it contains the lowest binding energies of both Si–O and Mg–O from Si–O–Mg bonds. For the catalysts calcined at low temperature (350 and 400 °C), more 1-butanol and C6 comp...

Abstract: During wine-making and aging, the phenolic composition gradually changes, mainly owing to oxidation reactions, which may result in a decrease in astringency as well as in color stabilization. Anthocyanins and tannins are the main compounds involved in these changes. The influence of enological tannins on the outcome of red wine oxidation has been evaluated in this study. Oligomeric tannins were added to red wine so as to have wines with three different anthocyanin A/tannin T ratios W (ratio 1A: 0.5T) WT (ratio 1A: 1T) WTT (ratio 1A: 3T). Samples were then treated with hydrogen peroxide to trigger the Fenton reaction. Chromatic characteristics, phenolic composition and acetaldehyde were monitored during oxidation. The samples treated with a higher concentration of tannins showed a clear improvement of color intensity with oxidation mainly due to an increase in polymeric pigments. The higher the content of tannins were, the lower the production of acetaldehyde. These are the first data showing the effect of different A/T ratios on the production of acetaldehyde during an oxidation process.

Abstract: An experimental kinetic investigation has been carried out for ethanol steam reforming (ESR). The selected catalyst was a K-promoted Ni/ZrO2 sample prepared by flame pyrolysis, which revealed particularly active and stable for this application based on previous investigation. Ethanol conversion, selectivity to the main possible byproducts (methane, ethylene and acetaldehyde), hydrogen productivity and the CO/CO2 ratio, as a measure of the contribution of the water gas shift reaction, were correlated to the temperature, water/ethanol ratio and space velocity in a central composite experimental design. The parametric dependence of the reaction outcomes helped the qualitative assessment of the best operating conditions and suggested hypotheses on the reaction mechanism. A more quantitative parametric analysis was carried out by multivariate analysis. Particularly dramatic experimental conditions have been adopted in order to highlight the formation and further evolution of possibly critical intermediates, such as ethylene and acetaldehyde. To keep ethanol and intermediates conversion below 100% at sufficiently high temperature to guarantee coke-free operation, the space velocity and feed dilution were increased. This will enable drawing a kinetic model accounting for the detailed evolution of such species. An increase of temperature did not adequately improved H2 selectivity, whereas the water/ethanol ratio was an effective parameter to push H2 productivity. The reforming reactions of ethanol and of acetaldehyde/ethylene byproducts were dependent on the three parameters (kinetically controlled), whereas the CO/CO2 ration was substantially independent on the space velocity, indicating that the water gas shift reaction reached an equilibrium value.

Abstract: Two cobalt catalysts, Co/SBA-15 and Co/SiO2, have been studied in steam reforming of ethanol (SRE). Besides the steam reforming products, ethoxide dehydrogenation to acetaldehyde is observed as one of the main reactions. Although by hydrogen treatment cobalt is reduced to the metallic state, under SRE conditions, a phase appears that has been identified as cobalt carbide and correlates with acetaldehyde production. These findings provide insights about the catalytic sites, for SRE, in cobalt catalysts. Comparison with previous results shows that these conclusions are not translatable to other cobalt catalysts, stressing the importance of the support on the catalytic behavior of cobalt.

Abstract: Formaldehyde and acetaldehyde are commonly found in cloud droplets because of reversible partitioning and hydration reactions. An SOA formation pathway was recently identified in which these common aldehydes are irreversibly incorporated into imidazole derivatives formed by reaction with dicarbonyl species and ammonium salts or amine species. Here we use ultraviolet–visible and nuclear magnetic resonance kinetic measurements to determine the influence of formaldehyde and acetaldehyde on aqueous methylglyoxal chemistry. The presence of formaldehyde increases imidazole product formation rates by factors of 2 and ≥5 in reactions with ammonium sulfate and amines, respectively, and increases imidazole product yields in methylglyoxal + amine reactions by more than an order of magnitude. Acetaldehyde is less likely to be incorporated into imidazole products and increases formation rates and yields only in reactions involving amines. We estimate that aqueous formation of imidazoles could generate as much as 1.05 ...

Abstract: The dehydrogenation of bioethanol to acetaldehyde and hydrogen is a sustainable process, owing to the atom-economical transformation and easy separation of the products. However, oxide-supported Cu catalysts show a low selectivity to acetaldehyde because of considerable side reactions caused by their oxygen-rich surfaces. A conventional carbon-supported Cu catalyst shows high selectivity, but is quickly deactivated due to the migration and agglomeration of copper particles. Here, we have produced a highly porous nitrogen-rich carbon support which contains 6.2 wt% N and can nicely disperse and stabilize Cu nanoparticles ~6.3 nm. When used for ethanol dehydrogenation, ~98% selectivity to acetaldehyde has been achieved, with excellent anti-agglomeration ability as long as 500 min. XPS data prove that electron transfers to Cu particles from N sites. Theoretical calculations further show the nitrogen-sites enhance the adsorption of Cu20 cluster and can stabilize them against coalescence, with graphitic-N sites (~40% of total N content) being the most significant.

Abstract: This study investigates the effect of double- or single-stage distillation and different alcohol content in ‘hearts’ (middle fractions) on the distribution of aroma volatiles and undesirable compounds (methanol, hydrocyanic acid, ethyl carbamate) during distillation of plum brandies. Irrespective of the distillation method used, the first fractions (‘heads’) included mainly aliphatic aldehydes, acetals and esters as well as higher alcohols (1-propanol, 2-methyl-1-propanol, 1-butanol, 2-methyl-1-butanol and 3-methyl-1-butanol). Furfural, 1-hexanol, benzyl alcohol, 2-phenylethanol and ethyl carbamate occurred in relatively high concentrations in the ‘tail’ fractions. Increasing the concentration of alcohol in the heart fractions from 70 to 90% v/v resulted in a gradual decrease in the concentration of all detected volatile compounds. Compared with single-stage distillation, double distillation produced heart fractions with lower concentration of acetaldehyde and benzaldehyde and with higher contents of furfural and esters, such as isobutyl acetate and isoamyl acetate. There was a statistically significant increase in the amounts of methanol and ethyl carbamate obtained from double distillation compared with similar fractions derived from the single-stage process. However, in all fractions these compounds occurred in concentrations much lower than the limits specified by EU regulations. The heart fraction from the double-stage process with 83% v/v alcohol content received the best scores for aroma and flavour. Copyright © 2017 The Institute of Brewing & Distilling

Abstract: The interaction of silver with the surface of CeO2 in the Ag/CeO2 catalysts prepared by coprecipitation and impregnation techniques was studied by temperature-programmed reduction, X-ray diffraction, and high-resolution transmission electron microscopy. It was shown that coprecipitation technique led to formation of strong silver–support interaction and the epitaxy of silver particles (d 111 = 2.35 A) on the surface of CeO2 (d 111 = 3.1 A). This provided incresed catalytic activity in the oxidative dehydrogenation of ethanol at relatively low temperatures (a 15% conversion of ethanol with 100% selectivity for the formation of acetaldehyde was reached at 85°C). Above 130°C, the deep oxidation of ethanol to CO2 becomes the predominant direction of a catalytic reaction, and the Ag/CеО2 catalyst obtained by impregnation technique was most active in this region as a consequence of the weaker metal–support interaction.

Abstract: The oxidation of ethanol to acetaldehyde in the fine-chemical industry is a burgeoning process that requires leading-edge technology. A major challenge is to find a catalyst with high ethanol conversion and high acetaldehyde selectivity at a high gas hourly space velocity (GHSV) and a low operation temperature. Boron nitride nanosphere supported Au–Cu nanoparticles offer much opportunity for low-temperature ethanol oxidation. A catalytic ethanol conversion of 77 % and a selectivity of 94 % towards acetaldehyde were achieved at a temperature of 180 °C and a high GHSV of 100 000 mL gcat−1 h−1, values that far exceed those obtained with Au–Cu/SiO2. The immobilized Au–Cu nanoparticles have an average size of approximately 3 nm, and the majority of Au species are assigned Auδ−. The weak interaction of acetaldehyde with both Au–Cu active phases and the boron nitride support facilitates the adsorption–desorption behavior of acetaldehyde. As a result, the progression of secondary reactions is slowed and the degree of coverage of the active sites is minimized.

Abstract: The color stability of red wines produced from interspecific hybrid grapes, which is partially dependent on anthocyanin diglucosides, is not well understood. In this study, the rate of decrease of monomeric anthocyanins as they polymerized to polymeric pigments due to the presence of excess catechin and acetaldehyde was measured in model wine using HPLC. Colorimetry was used to measure L*, a*, and b* values, hue angle, and change in color (ΔE). Concentrations of individual diglucosides decreased more slowly than monoglucosides. When monoglucosides and diglucosides were combined, the reaction rate of monoglucosides was slower than that of monoglucosides alone. Hue angles described transitions from red to red-orange, orange, or orange-yellow as anthocyanin-specific changes occurred. The evolution in color represents dynamic reactions between anthocyanins, catechin, and acetaldehyde. Consequently, wines containing high concentrations of diglucosides, such as those produced from interspecific hybrid grapes, w...

Abstract: Alcohol consumption is a serious health issue in Korea in terms of the amount consumed and the behavior related to its consumption Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme in alcohol metabolism that degrades acetaldehyde to nontoxic acetic acid The enzyme is coded by the ALDH2 gene, which is commonly polymorphic in East Asian populations A point mutation in the ALDH2 gene (the rs671 allele) yields an inactive form of ALDH2 that causes acetaldehyde accumulation in the body after alcohol consumption, thereby inhibiting normal alcohol metabolism Individuals who are homozygous for polymorphism in ALDH2 tend to refrain from drinking alcohol, decreasing their chances of developing alcoholism and exposure to the associated risks Mendelian randomization (MR) studies have demonstrated that alcohol consumption predicted by ALDH2 genotype is causally related to cardiovascular risks Moreover, recent MR studies suggest that the ALDH2 variant has mechanistic effects on some disease outcomes or mortality through increased blood levels of acetaldehyde, showing differences therein between heterozygotes (ALDH2*2*2) and homozygotes (ALDH2*1*2) in those who consume alcohol Accordingly, consideration of ALDH2 genotype in alcohol prevention programs is warranted In conclusion, strategies that incorporate genetic information and provide an evidential basis from which to help people make informed decisions on alcohol consumption are urgently required

Abstract: Acetone is an important solvent and widely used in the synthesis of drugs and polymers. Currently, acetone is mainly generated by the Cumene Process, which employs benzene and propylene as fossil raw materials. Phenol is a co-product of this synthesis. However, this ketone can be generated from ethanol (a renewable feedstock) in one-step. The aim of this work is to describe the influence of physical–chemical properties of three different catalysts on each step of this reaction. Furthermore, contribute to improve the description of the mechanism of this synthesis. The acetone synthesis from ethanol was studied employing Cu/ZnO/Al2O3, Ce0.75Zr0.25O2 and ZrO2. It was verified that the acidity of the catalysts needs fine-tuning in order to promote the oxygenate species adsorption and avoid the dehydration of ethanol. The higher the reducibility and the H2O dissociation activity of the catalysts are, the higher the selectivity to acetone is. In relation to the oxides, these properties are associated with the presence of O vacancies. The H2 generation, which occurs during the TPSR, indicates the redox character of this synthesis. The main steps of the acetone synthesis from ethanol are the generation of acetaldehyde, the oxidation of this aldehyde to acetate species (which reduces the catalyst), the H2O dissociation, the oxidation of the catalyst producing H2, and, finally, the ketonization reaction. These pieces of information will support the development of active catalysts for not only the acetone synthesis from ethanol, but also the isobutene and propylene syntheses in which this ketone is an intermediate.

Abstract: Summary Ethanol is an important target for the renewable production of liquid transportation fuels. It can be produced biologically from pyruvate, via pyruvate decarboxylase, or from acetyl-CoA, by alcohol dehydrogenase E (AdhE). Thermophilic bacteria utilize AdhE, which is a bifunctional enzyme that contains both acetaldehyde dehydrogenase and alcohol dehydrogenase activities. Many of these organisms also contain a separate alcohol dehydrogenase (AdhA) that generates ethanol from acetaldehyde, although the role of AdhA in ethanol production is typically not clear. As acetyl-CoA is a key central metabolite that can be generated from a wide range of substrates, AdhE can serve as a single gene fuel module to produce ethanol through primary metabolic pathways. The focus here is on the hyperthermophilic archaeon Pyrococcus furiosus, which grows by fermenting sugar to acetate, CO2 and H2. Previously, by the heterologous expression of adhA from a thermophilic bacterium, P. furiosus was shown to produce ethanol by a novel mechanism from acetate, mediated by AdhA and the native enzyme aldehyde oxidoreductase (AOR). In this study, the AOR gene was deleted from P. furiosus to evaluate ethanol production directly from acetyl-CoA by heterologous expression of the adhE gene from eight thermophilic bacteria. Only AdhEs from two Thermoanaerobacter strains showed significant activity in cell-free extracts of recombinant P. furiosus and supported ethanol production in vivo. In the AOR deletion background, the highest amount of ethanol (estimated 61% theoretical yield) was produced when adhE and adhA from Thermoanaerobacter were co-expressed.